1. Field of the Invention
This invention relates generally to a device used in the treatment of neurological disorders, especially pain and motor disfunction by electro-stimulation of nerve fibers of the spinal cord, and more particularly to a novel combined assembly of an electrode and lamina hook which is more reliable in maintaining the position of the electrode relative to the target fibers of the spinal cord.
2. Description of the Prior Art
The use of electrical stimulation for the purposes of alleviating pain and the treatment of other neurological afflictions has been utilized for a number of years, and in many instances has become the standard of care. In new applications, as well, electrical stimulation of components of the nervous system continues to show significant therapeutic promise.
More particularly, in the spine, the original approach to electrical stimulation was to place multiple electrical leads directly onto the dura around the spinal cord. In such a procedure, the laminae of a sequence of vertebrae were removed so that the leads could be placed in a spaced apart relation along the central posterior axis of the spinal cord. This approach required a substantially invasive procedure in which bones and tissue were displaced or removed. In addition, the high frequencies of electrode migration from the target site or sites rendered the entire procedure suspect.
Subsequent iterations of spinal cord stimulation devices were implanted much less invasively, generally by percutaneous positioning. The first generations of this approach were immediately advantageous over the prior methods, insofar as they were carried out using local anesthetic as the electrodes were guided into position with the use of a fluoroscope. These early non-invasive procedures continued to use single lead electrodes, thus requiring a plurality of separate implantations. In addition, the leads would still easily become dislodged and migrate from the desired treatment site, usually becoming ineffective, but sometimes having actively negative effects on other nerves. These limitations and failures associated with multiple implantations of single lead electrodes briefly caused a reversion to the older, more invasive approach.
In an attempt to unify the multiple leads necessary for spinal cord stimulation into a single electrode, thereby attempting to bring the state of the art back to non-invasive procedures, designs from the cardiovascular art, i.e. pacemakers, et al., were modified for use in the spine. Multiple lead electrodes had been used in the cardiovascular field for some time, and were generally designed to provide stimulation to a variety of points on the surface of the heart. The modifications of these leads included strengthening the both the leads and the structure containing the leads for the stresses of the spine, reducing the diameter of the leads to a size more appropriate for use in the spine, and alternatively providing either a removeable or permanent rigid wire within the electrode to enhance placement. Unfortunately, while eliminating some of the causes associated with electrode migration, and reducing the number of electrodes which could migrate, the advances did not address the fundamental inability to fix the electrode at the appropriate location. This problem has been, and continues to be a significant drawback to the use of spinal cord stimulation in the regular treatment of pain.
Accordingly, it is an object of the present invention to provide a spinal cord stimulator assembly which reduces the incidence and complications associated with the migration of the electrode.